All VHF marine band radios operate in the simplex mode，which means that（）.

A.only one person may talk at a time

B.only two persons may talk at the same time

C.the radio only transmits

D.the radio only receives

商务旅行计划制定后，应该交给（）。

A.出差的上司一份

B.其他部门的经理一份

C.存档一份

D.出差上司的家属一份